1. Field of the Invention
The present invention relates to a method of, and demodulator for, digitally demodulating a single sideband (SSB) signal.
2. Description of the Related Art
Digital demodulation of an SSB signal is known, for example, from an article entitled "Digital HF Radio: a sampling of techniques" in Ham Radio magazine, April 1985, page 18 et seq., particularly FIGS. 14-16 on pages 31 and 33 and the corresponding description. Typically an IF signal is filtered and applied to an analogue to digital converter (ADC). The ADC output signal is then processed digitally inter alia by effectively creating two quadrature-relating channels by means of quadrature mixers, low-pass filtering and decimating the signals in the two channels, and filtering and arithmetically combining the results. The results of the arithmetic combination may be reconverted to an analogue signal in a digital to analogue converter (DAC). An advantage of processing a signal digitally is that a more flexible or general purpose demodulator can result. However the known methods are liable to require particularly stringent filtering which means that dedicated circuits may have to be made for each stage of the demodulator.